Prince speaks onstage during the Grammy Awards in 2015 in Los Angeles.

When Prince reached out to Dr. Howard Kornfeld, a California-based chronic pain and addiction specialist, Kornfeld wasn't immediately available to go see him. Instead, the doctor put his son Andrew on a plane to Minnesota to deliver the singer's buprenorphine, a drug used to treat opioid addiction.

That was a big mistake, experts say.

"If it's an emergency, call 911, for God's sake," Dr. Mark Willenbring, a former director of treatment research at the National Institute on Alcohol Abuse and Alcoholism, told The Associated Press. "Don't send your pre-med son on a redeye."

While it's possible the pop icon contacted an out-of-state addiction expert for privacy reasons, Willenbring noted that his own office is a mere 20-minute drive from Paisley Park, and said he's authorized to prescribe buprenorphine, which is a controlled substance in Minnesota.

Prince died in April at age 57, after Kornfeld's son arrived at the singer's home to find him unresponsive in an elevator and subsequently called 911.

Authorities investigating Prince's death found prescription pain medication on Prince's person and in his home, and called in the Drug Enforcement Administration to assist with the case, CNN reports. The singer suffered from hip and knee pain from years of jumping up and down in high heels while performing, singer Sheila E., a longtime friend, told the AP.

Prince’s four-hour autopsy was completed in April, and authorities delayed releasing his cause of death until the toxicology report was complete. On Thursday, the Midwest Medical Examiner’s Office tweeted the investigation results, which revealed that the singer died of a self-administered overdose of the opioid fentanyl.

How Compassionate Doctors Created A Culture Of Addiction

It all started with good intentions. Following reports from doctors in the 1980s that opioids were safe and addiction was a rare side effect, drug companies rushed to advertise them as a solution for chronic pain in the 1990s.

“There is a growing literature showing that these drugs can be used for a long time, with few side effects and that addiction and abuse are not a problem,” Dr. Russell Portenoy, then a pain specialist at the Memorial Sloan Kettering Cancer Center, told The New York Times in 1993.

Portenoy would go on to be named the president of the American Pain Society, which in 1996 classified pain as the “fifth vital sign” alongside body temperature, blood pressure, heart rate and breathing rate.

What Happens To Your Body When You Overdose On Opioids

It’s important for health care providers and family members to carefully watch people who are prescribed opioids, Dr. Nitin Sekhri, the medial director of pain management at Westchester Medical Center, told The Huffington Post.

Not only can patients become addicted, but they often underestimate the effect of drug interactions that can occur even with run-of-the mill medications like antibiotics, which inhibit the enzyme that breaks down some medications and can actually lead to overdose.

Even a mild infection can have disastrous impact on opioid users. “It lowers someone’s threshold for respiratory depression,” Sekhri explained, noting that having a fever is akin to taking a narcotic in some cases, and can impact breathing.

One of the telltale signs that someone is overdosing on opioids is that he or she becomes lethargic, sometimes to the point of being sleepy and unable to wake up.

“They start to breathe very, very, very slowly, to the point of maybe stopping breathing,” Sekhri said.

“When you stop breathing, you build up carbon dioxide and you lose oxygen content in your body. That can put a huge strain on someone’s heart, and they can go into cardiac arrest from having low oxygen,” he said. “Obviously, this can be deadly.”

From Prescription Pain Treatment To Heroin Addiction

The risk of taking opioids isn’t limited to overdose. There’s a well-trod path from opioid use to opioid misuse to heroin addiction.

“Our health professionals’ well-intentioned approach to treating people’s pain can sometimes lead to unintended consequences and exposing an individual to the risk of addiction or overdose,” Dr. Hillary Kunins, assistant commissioner at the New York City Department of Health and Mental Hygiene, previously told HuffPost.

For recovering opioid addicts, getting treatment presents its own obstacles. Buprenorphine, which blocks withdrawal effects and craving ― and which Andrew Kornfeld was en route to deliver to Prince ― is one of the best treatments for opioid addiction. Unfortunately, there is a shortage of doctors in the U.S. who are certified to prescribe buprenorphine to patients.

"We’re in a watershed moment in chronic pain management in the United States," Sekhri said. "The jury is out right now on how to move forward, but undoubtedly opioids are a part of chronic pain management."

Helping Loved Ones Struggling With Addiction

If you think your loved one might be abusing legally prescribed opioids, don't be shy. "If a family member feels that someone is misusing [legally prescribed opioids], you have to call the prescriber," Sekhri said. "That is far and away the first and most important thing."

More and more states have databases for controlled substances, and some even have cross-state registries. "I can actually look and see if someone has been prescribed in New York and New Jersey," he said. "We can find out who is quote-unquote 'doctor shopping.'"

Signs to look out for include pinpoint pupils, problems with the law and lethargic behavior, particularly if someone extroverted becomes introverted and starts sleeping a lot, Sekhri added.

If someone is misusing pain pills without a prescription, he or she needs to see a mental health professional who specializes in addiction issues.

"I tell patients who are addicted to opioids that this is a lifelong battle, just like having hypertension or having cancer," he said.

While that might seem like a pessimistic outlook, Sekhri says patients who have been ostracized because of their addiction are relieved to hear that addiction is a medical condition, not a personal failing or a lack of willpower.

"It’s something where you’re going to have remission and you are going to have relapses, just like multiple sclerosis, just like other problems," he explained. "At times, it’s going to be poorly controlled. You have to fight through through those times. It’s a very difficult, lifelong struggle."

Do you or some someone you know need help with substance abuse or mental health issues? In the U.S., call 800-662-HELP (4357) for the SAMHSA National Helpline.